Documentation: document the ABI changes for KVM_CAP_ARM_MTE

Document both the restriction on VM_MTE_ALLOWED mappings and
the relaxation for shared mappings.

Signed-off-by: Peter Collingbourne <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Reviewed-by: Cornelia Huck <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: pcc

Documentation/virt/kvm/api.rst

@@ -7385,8 +7385,9 @@ hibernation of the host; however the VMM needs to manually save/restore the
 tags as appropriate if the VM is migrated.
 
 When this capability is enabled all memory in memslots must be mapped as
-not-shareable (no MAP_SHARED), attempts to create a memslot with a
-MAP_SHARED mmap will result in an -EINVAL return.
+``MAP_ANONYMOUS`` or with a RAM-based file mapping (``tmpfs``, ``memfd``),
+attempts to create a memslot with an invalid mmap will result in an
+-EINVAL return.
 
 When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to
 perform a bulk copy of tags to/from the guest.